The CLEO-c and the two B factories already give more measurements of
charmed meson decays than ever. The BESIII and super B factories are
going to give even much more data soon. Therefore, it is a good
chance to further study the nonleptonic two-body \(D\)  decays.
However, it is theoretically unsatisfied since some model
calculations, such as QCD sum rules or Lattice QCD, are ultimate
tools but formidable tasks. In \(B\)  physics, there are QCD-inspired
approaches for hadronic decays, such as the perturbative QCD
approach (pQCD),[1]} the QCD factorization approach
(QCDF),[2]} and the soft-collinear effective theory
(SCET).[3]} But it doesn't make much sense to apply these
approaches to charm decays, since the mass of charm quark, of order
1.5 GeV, is neither heavy enough for a sensible \(1/m_c\)  expansion,
nor light enough for the application of chiral perturbation theory.
